The present invention relates to valves and pertains more particularly to closed centered pressure compensating control valves.
Some hydraulic machines have implements and systems which must undergo frequent adjustment to various fixed positions where they remain fixed for periods of operation. In other words, the hydraulic system is primarily for adjustment of machine implements rather than operation thereof. One example of such machines is a motor grader. Present motor graders normally employ open centered circuits with a pump delivering a constant flow of fluid at all times.
Considerable horsepower could be saved in such machines if pump flow could be reduced or cut back during periods when the control valves are in neutral.
Open centered circuits also have the disadvantage of being more sluggish and less responsive than closed centered systems.
Such vehicles also employ a number of different circuits having different flow requirements. These circuits are normally controlled from a bank of four or five valves. Because of the different flow requirements, the valves are sometimes quite different in size and construction.